The present invention concerns a mounting arrangement of the bars supporting the grippers in a map-making machine, and more specifically a machine for printing security-paper, particularly a color printing machine.
It is known that, in map-making machines of this type, the paper to be printed, or already printed, is in single sheets being conveyed one by one, in succession, between printing rolls or other processing means. Due to the nature of the product being treated, it is known that a very high precision--for example of the order of a few millimeter tenths--is required in conveying the single sheets.
The paper sheets are drawn singly from a feed pile, are conveyed along the machine by means of rolls or other devices and, at the end of an intermediate travelling path, they are clamped by grippers mounted on one or more bars and are conveyed to the outlet of the machine.
Each of these bars actually consists of a pair of parallel rods, one of which is simply adapted to support a plurality of parallel grippers, while the other one is also adapted to control the opening and closing of the grippers.
Said rods are normally supported, at their opposite ends, on a pair of transport chains moving along a closed ring path.
The assembly is usually quite simple since said rods, which have a tubular configuration, are engaged with their ends in the transport chains merely by way of pins.
This transport system--which has proved up-to-date fully satisfactory as to its precision in conveying the paper sheets in map-making and, specifically, security-paper printing machines--suffers however from quite a serious drawback: when, accidentally, one or more sheets of paper, or a foreign matter, cause jamming along the travelling path, which can also damage the aforecited transport grippers, the necessary maintenance operation to eliminate the jamming turns out to be extremely difficult.
In fact--bearing in mind that each rod is mounted with precision between two transport chains sliding with precision along two fixed parallel guides--it can be easily understood how, in order to disassemble the rods, it is necessary to remove at least one of the two chains from its slide guide, and often both chains.
However, taking into account that--as stated above--said guides essentially form a closed ring path, it is evident that they also need to be removed in order to allow removal of the chains. This operation could be merely toilsome--for the guides positioned in some of the more easily accessible areas of the machine--but it can even become impossible unless other parts of the machine are first removed.